It is not necessarily the very largest schools winning every year, but if you look at
the winners and runners up in D1 the list tends toward the largest schools. It is even more telling if you look at the top five teams year by year.
I know a college professor/runner/track&XC parent who is working on a paper analyzing the effect of school size on cross country. I have seen an alpha version of his analysis and it is very clear that school size is a huge factor. No one is arguing, for either sport, that having a big school is a sufficient condition for having a good team. But it is pretty clear that it is a dominant factor.
I coach at Coffman, which is ranked somewhere in the mid 30s in school size for boys, a little over half the enrollment of Mason and mid 40s with half of Mason's enrollment for girls. Taylor's enrollment is proportionally much closer to ours than the bottom schools are to the top schools in D1. In the last dozen or so years, how many years did Taylor have a track team that could beat Coffman's for boys or girls? Not very many. Same thing with XC. I would NEVER argue that I am a better coach or that we have a better coaching staff than Taylor. We have a lot more students.